We would highly advise against processing live transactions on your own store as this can be seen as fraud. If you intend to test the checkout process then you will want to use the "test" mode for Shopify Payments or set up the "bogus" gateway as outlined here.
Would you mind sharing a screenshot of the error you're getting? If you open the order in Orders/Abandoned Checkouts and scroll to the timeline, are you able to see a failed payment line? If yes, you can click to expand the information as this should reveal why the payment type was rejected.
Thank you for the context! The issue is with the amount you are trying to charge. You will need to test a higher amount typically more than 50 cents in order for the charge to go through.